Telephone system



l. MOLNAR TELEPHONE sIYsTEM k Aug. 7',

Filed Aug. v28, -1944 6 Sheets-Sheet l Mfla INS. GEN.

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TRUNK FIG. I

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RINGING im? I INVENTOR. -IMRE MOLNAR Aug. '7, 1945; I. MOLNAR 2,381,769I TELEPHONE SYSTEM Filed Aug. 28, 1944 e shets-sheet :s

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/LIIT 'OUTGOING :SELECTOR I Aug. 7, 1945. L MQLNAR 2,381,769

TELEPHONE ySYSTEM Filed Aug. 28, 1944 6 Sheets-Sheet 4 i I 200A; F|G 4Bgmfol` I 204, l f25 y M Elli T 1.. ,WYSTA.

s R G P ATER WAYSTA. WAYS-TA. RE E INVENTOR.

IMRE MOLNAR ATTORNEY Aug. 7, 1945.

l. MOLNAR TELEPHONE SYSTEM Filed Aug. 28,"1944 e sheets-sheet 5INVENTOR* mms MoLuAR A ATTORNEYv Filed Aug. 28, 1944 6 Sheets-Sheet 6FIG-7. Fleas` 24|, 22a* i l Y;

. l l' VT Y INVENTOR. IMRE MOLNAR y' ATTORNEY n Patented Aug. 7, 1945TELEPHONE SYSTEM Imre Molnar, Chicago, Ill., assignor to Automatic lElectric Laboratories, Inc., Chicago, Ill., a poration of DelawareApplication Aug-ust 28, 1944,Serial No. 551,489

2,8 Claims.

\ The present invention relates in general to automatic telephonesystems, and more particularly to multi-exchange systems in which thedifferent exchanges are connected by trunk lines connected at each endto an automatic two-way impulse repeater, and inwhich control isexercised over a ground return `circuit superimposed on theinterconnecting trunk lines.` These ground return control circuits`aremost often employed on long-trunks in order to reduce the effectiveresistance and may be arranged for either simplex or compositeoperation, the former utilizing both sides ofthe trunk in parallel, andthe latter using only one leg of the trunk, with suitable arrangementsto `prevent interference between control and speech circuits.

In such systems it may and often does, happen that the batteries at thevarious exchanges are at diierent potentials, or that theexchangegrounds are at different potentials, and that these dif'- ferences inpotential between two given exchanges may be such as to cause falseoperation of the control equipment under certain conditions, particularly when thesystem is at rest, with both ends of the control trunknormal and ready to receive signals.`

The-main object of my invention' is therefore the provision of simpleAand inexpensive means at theterminalrends of the control circuits topreventthe iiow of current over these circuits due to the presence ofunbalanced potentials aspreviously described, during periods when nocurrent is supposed to ow. It is known that methods have been devisedfor `neutralizing or offsetting the effects of such `potentialdifferences in trunk circuits, but most such systems require the use ofa separate neutralizing conductor, cr are quite expensive, or both,whereas the method here described operates over the regular controlconductors, is low in cost, and adds no complexities to the circuits. e

Another object ofthe invention is to provide improved repeaterand trunkarrangements of the character described, wherein magneto telephonewaystations may be insertedin the trunk circuit, with facilities wherebythe various waystations may call one` another, make calls through therepeater at either end of the trunk and into the associated automaticexchange, or receive calls from either exchange through the associatedrepeater. 7

'I'he main feature of the invention lies in the provision of aunidirectional current conducting device suchas a copper oxiderectiiier, in the circuit between the line battery terminals and thecontrol relays directly associated withthe ground return controlcircuits in each repeater.Y These control circuits, which permit twowayv operation, supervision and release through the repeaters at theends of the trunk by the Well knownV method of changing the'connectionsfrom battery to groundor vice versa at each end of the control `circuitas required, are thereby guarded against the eiectof differences inbattery or ground p otentials,as previously indicated.l These rectifierdiscs may be connected in series with either `cr both sides of the linebattery,-and separate discs would normally be provided for the controlrelays of each trunk, `where Jmore .l than one` trunk: is employed. Theuse of common groups of discs for more than one trunk is also possiblehowever, as `will be described later, and either arrange-- inentwillfall within the intended scope of the invention. l r

Another feature of the invention in connection with the potentialguarding arrangement lies in the fact that this feature does not dependon any particular type of, trunk, or on any Ispecial arrangement oftherground-.return control circuits, but can be applied toalmost `anysystem of this nature, by simpleinsertion, without vother change.` It isfor` example,` `equally applicable to simplex or composited trunks,'whetherv automatic or manual. It isalso applicable'torduplex telegraphcircuits operating over `composited trunk lines. This universalityderives from the fact that it operates over theregular controlconductors, without effecten thefnormal` control functions. y. I y Y Afurther feature of the invention consists fin the arrangement permittingthe; use of waystaf tions in a simplex trunk circuit between twofautonmatic exchanges witha two-wayA automaticI 'rcpeater at each 'end of thetrunk, an'd'fthe provi# sion in each repeaterof "ag code switch for sigFnalling the waystationsk ,by means oiv automatic code ringing, inaccordalncewith the number dialed. A Still another feature of theinvention provides for the instantaneous busying of the ,repeater at theother end of the trunk on such 'a call, and in the grounding of thetrunk by the called Waystationupon answering, in order to cut off thering. Both repeaters are made busyfon callsb'etween exchanges, oncalls'between either exM change and a waystation, either to or' from'the waystation, and on calls between Waystations. This last type of calldoes not" affect the repeaters otherwise. g Other features of theinventionvwill be apparent from the following specification, havingreference to the accompanying drawings, comprising Figures 1 through 10.

Figures 1, 2 and 3 of the drawings show the circuit of the automatictwo-way, simplex-dialing, code ringing repeater required at each end ofthe trunk for extending and receiving calls, and for signalling thewaystations. For convenience in following the operation, the threesheets comprising the complete circuit should be placed side by side inthe order named, with the 4 interconnecting leads properly aligned.

In Figure 1, the trunk end of the repeater, the

incoming end of a simplex trunkcomprising conductors I and 2 is shown inthe upper portion of the sheet, suitably terminated in the repeatingcoil A. At B in the lower left portion of this sheet is the code switchwhich selects the ringing code to be applied to the trunk on calls to away-- station. This is a ten point stepping switch capable of followingdial pulses commonly known in automatic telephone practice as a minorswitch, and is provided with stepping and release magnets and off-normalsprings as indicated. The bank contacts of this switch are shownconnected to the code ringing equipment C, com-r prising a source ofalternating ringing current and an automatic code interruptor, withstarting control therefor vested in the repeater. When in operation,grounded ringing current from the ringing machine passes through vthecode interrupter which breaks it up into long and short pulses, andimpresses it on the banks of the code selector switch in the form of astandard ringing code,l a different code being applied to each bankcontact. This vpermits impressing different ringing codes on the trunkon waystation calls by positioning the code 'selector switch on theproper bank contact, which occurs automatically when the waystationnumber is dialed.

Figure 3 shows the exchange end of the repeater. As indicated conductors3, 4, 5, 6, I and 8 are connected to the banks of one or more selectorssuch as E to permit the seizure of the repeater for outgoing calls,While conductors 9, I and II are connected to the operating end of anincoming selector D. VThese selectors may be considered as being twomotion automatic switches of the well known Strowger type, having tacts,represented by horizontal lines beneath the selector, each linerepresenting I0 contacts. In practice the holding or busying conductors5, -8 and II would be connected to a separate bank of the same switch,but in the drawings both banks have been combined into a single bank,for simplicity. It should be noted that conductors 3, 4 and 5 areconnected to a dierentbank level in selector E than conductors', 1 and 8in order to provide two points of access to the repeater on outgoingcalls, one for through calls to the distant exchange, and one for callsto a waystation. The code selector switch is automatically cut into thecircuit in the second case but not in the first case, whiledialing onthe trunk occurs only in the first case.

In Figure 4 is shown a diagrammatic representation of the trunk layout,the square G representing the repeater at one end of the trunk, R., Sand T the waystations, and conductors I and 2 the trunk conductors. Theopen conductors I and 2 at the edge of the sheet may be considered asleading to the trunk conductors I and 2 of Figure 1. If therefore Figure4 is placed to the left of Figures 1, 2 and 3 with conductors I and 2aligned the complete circuits will be shown by the four gures, Figures1, 2 and 3 being the repeater at the other end of the trunk identicalwith repeater G. V, i i y In square T of Figure 4' is showna typicalcircuit of one of the magneto telephone waystations, and the method ofconnecting it into the trunk line. Trunk splitting keys for opening vthetrunk in one direction when dialing in the other direction from thewaystation are indicated at 200`and 20|. A hand generator is shown at202, a ringer at 203 and dial impulsing and Ashunt springs at 204 and205. The hook switch `is provided with two sets of springs 206 and 201,

and has two operated positions. When the receiver is removed the hookswitch operates only part way, closing contacts 200 and connecting thereceiver 208 andthe transmitter 200 to the trunk. Complete operation isby a hook latch indicated at 2I3. Upon the tripping of 4this hook latchby the subscriber, the hook switch operates fully and closes contacts201,' vwhich connect ground to the center point ofthe ringer and thenceto both sides `of the trunk in parallel. The hook latch is automaticallyreset upon restoration of the receiver, as are the trunk splitting keys.

Figure 5 shows the basic arrangement of the potential guarding" schemeasl applied to the simplex trunk of `Figulell guard against differencesin battery potential while the system is at rest' with both ends of thecontrol circuit connected to negative battery, are shown solid at 24|and 24 I Additional rectifiers are also shown dotted inthe ground sideof they battery at y25| tand 25| for guarding against the eifect ofdiierences of ground potential when both ends of the control circuit areconnected to this side of the battery. As previously indicated, eitheror bothsets of rectiers may be employed, as conditions'warrant. Y

In this ligure, the-trunk'conductors, which are common to both speechand control'circuits are shown at 20|v and'202. ',Thei control4circuits'are connected to thetrunk through'coils 220 and 220', whichare not affectedby voice currents and by their impedance exclude thesefrom the control circuits. The -condensers in the trunk side of therepeating coils A and A "on the other hand, prevent'the passage of"control currents from one leg of the trunk to the other, but per-J mitpassage of voice. currents.

The control circuit isshown in thenormal position, with both ends'connectedv to the negative terminals of their respective line batteriesthrough relays 228 and 228. Under this condition no current should ow,and the relays should remain at normal. If the battery potentials arenot thesame at any given 4vtime however, current will .tend to flow overthis circuit. This will be prevented with thel arrangement shown, by oneof the rectie'rs24lv or 24|* depending on the direction of lthecurrent''owgit being understood that current will lowv through vthe4rectiers in the direction of the arrow head, but' not in the oppositedirection. 'I

Similarly, lifrelays 235'a'nd A235', which are controlled from othercircuits in the repeater not shown, are operated atthe same time.as'they are during conversation,.both ends of thecontrol circuit areconnected to the ground terminals of vtheir respective line batteries,vthrough The rectiers whichrelays 229 and 229,'. Under thisconditionagain, no current should iiowvand therelays should not operate,or if previously operated should release. Differences in` groundpotential however would tend to cause current to iiow'and perhapsinterfere with the proper operation and release of these relays. iInsertion of rectifier discs as at 25| and 25| in this circuit wouldprevent this in the same manner as explained for discs 24| and 24|. Withrelay'235 operated and 235 normal, ground is connectedto the left end ofthe control circuit and battery to the right end of the circuit. Therectifiers are without eiTect since the arrow heads 4are now in thecorrect direction, and full battery current flows, operating relays 229and 228. Similarly, if relay 235 is operated and 235 normal', groundthrough relay 229' is connected to the right end of the circuit andbattery through relay 228 to the left end of the circuit, causing fullbattery current to now in the opposite direction to operate relays 229'and 228, again without interference from the rectiiiers.

Figure 6 shows the same potential guarding arrangementr applied to theMorse or control leg of a composited trunk. As is well known, this typeof trunk provides a separate control 'circuit over each side of thetrunk such as conductor 302. by means ofA condensers and retard coilssuch as indicated at 303, 304,` 303 and 304" which serve to keep thecontrol currents out of the voice circuits," andtvoice currents out'ofthe control circuits. The numerals 338 and 338 indicate a standard formof differential relay connected to each end of the control conductor 302over one winding and to an artificial balancing line and biasing circuitsuch as shown at 305 and 30,6,

` over the other windingsaid articial line having 'erationof the system,by relays 335 and 335",

under control of other circuitsnot shown. Rectier discs in both sides ofthe battery are indicated `at 301, 308, 301" vand 308'. Protective lamps`are shown at `309 and 309', and thump killing reactorsat 3|0 and 3l0'.

WithV the system at normal as shown, and ground on both ends Aof thecontrol circuit, a local current will flow from ground to batterythrough the lower winding of the differential relay and the artificialline. This biases the differential relays to their released position. Nocurrent should flow over the control circuit comprising the upperwinding of the relay and-the trunk conductor 302'. In the case ofdiffering ground potentials, current will tend to flow in this circuitbut will be prevented by the rectiiiers 308 or 308', in the mannerpreviously described.

If pole changer relay 335 is now operated, it will connect negativebattery to that end f the control circuit, and full battery current willliow over conductor 302 to operate the distant differential relay 338.The local differential relay will not operate at this timedue toopposing polarities in its windings. If now pole changer relay 335' isoperated, it will connect negative battery to the other end of thetrunk, stopping the current ilow over conductor 302. This will cause theoperation of differential relay 338 without releasing relay 338' sinceneither relay is now biased to the release position. In the case ofdiffering battery potentials, current will tend to ow over conductor 302at this time, but will be prevented by the rectiiiers in the batteryside of the circuit. The operation is similar in either direction.

Figures '7 and 8 show two methods of connecting the rectier discs intosimplex control circuits when twoor more simplex` trunks such as shownin Figure 5 are involved. It will be noted that thesetwo figures are thesame asthe left end of the control circuit of Figure 5 except for havingadded connections to a Asecond trunk. The same reference numerals areemployed -for this reason, 228` and 229 being the control relaysassociated with thev first trunk, and 2282 and 2292 being the' controlrelays associated with a second like trunk at the same exchange. Figures'7 and 8 are similar to each other except that in Figure '1 separaterectifier discs are shown in the circuit of each relay, while in Figure8 a common disc or group of discs `is employed in each side of thebattery and multiplied to the various relays as indicated'.

Figures 9 and 10 similarly show the same two methods of connecting thediscsl into two or more control circuits associated with compositedtrunks such as shown in Figure 6. These ngures are the same as the leftportion of the control circuit of Figure 6 except for the multiple trunkconnections and the omission of the artificial line, anduse the samenumeraldesignations 338 being the differential relay in the firstcontrol leg,- and 3382 a similar relay associated with a second controlleg in-the same exchange. Figure 9 shows individual discs and Figure 10shows common discs.

A detailed description of the operation of the repeater .and waystationcircuits as shown in Figl ures 1, 2, 3 and 4 will now be given, in orderto provide a complete'disclosure of the invention. It should beunderstood however, thatthe arrangement shown is representative only,and that minor modifications could be made therein without departingfrom' the spirit of the invention.v

Repeater to repeater call outgoing Under this heading the action of therepeater at the originating exchange on a through call to the distantexchange will be considered. On such a' call, the first part of thenumber dialed by the calling party will cause an outgoing selector suchas shown at E inA Figure 3 to raise yits wipers to the through switchinglevel here indicated as level 0, and tohunt and seize an idle repeatersuch as that shown, the line wipers being thereby connected to thetalkingT conductors 3 and 4, and the busying or holding wiper tobusyingconductor 5 ofthe repeater.

Ground from the busyingy wiper is now passed forward to conductors 5 and42 and thence through the upper winding of theI pole changing relay 35to'battery. This `winding alone however, does not have sufficient `powerto operate relay 35 which therefore remains normal. A branch of thissame circuit also extends over conductor 43 through the normally closedcontacts 44 of relay 30, the normally closed contacts 45 of relay 32,

l and the winding of switching relay 33 to negative battery. l

Switching relay 33 operates over this circuit and locks direct to theground on the busying conductor 5 by way of its make contacts 46. Relay33 at its contacts 41 disconnects the incoming` selector D from thecircuit by opening conductor l0, and at its contacts I49 and 53 connectsthe out ward pulsingl relay 21 to the local calling loop over thefollowing circuit: ground through the lower winding of relay 21, thenormallyclos'ed contacts 48 of relay 3|, make contacts 49 of theoperated relay 33, conductor 50, winding ofthe repeating coil A,conductor loop conductory 4 to the bank of selector E, throughtheoallingloop and back overV loop conductor 3, winding |0| of therepeating coil, conductor 52,'make contacts 53 ofv relay 33,: normally.closed contacts 54 of relay 3|, and the upper winding of relay 21 tonegative battery. Relay 21 operates Aover this circuit to busy therepeater and prepare it for dialing.

Switching relay 33 at its back contacts 55 also disconnects negativeline battery from the trunk preparatory to the grounding of the trunk toseize the distant repeater. As previously stated, the repeater maintainsnegative battery on the trunk when at normal. This circuit is asfollows: line battery from Figure 1, rectifier disc 4|, lconductor 56,upper winding 0f control relay 28, conductor 95, break contacts 51 ofrelay 38, break contacts 58 of relay 35, conductor 96, break contacts 55of relay 33, conductor 59, break contacts 60 of relay 22, both windingsof the simplex relay 20, windings |02 and |03 of the repeating coil,back contacts 6| and 62 of relay 23, back contacts 63 and 64 of `relay2|, and trunk conductors I andy 2 in parallel. With a similararrangement at thedistant end of the trunk negative battery encountersnegative battery and no current flows, the rectifier discs, aspreviously explained acting to prevent current flow should thebatterypotentials vary at times.

Operation of the outward pulsing relay 21 causes the operation ofrelease relay 32 from ground at make contacts 65, and also connects lineground to the trunk through control relay 29 over the following circuit:line ground from Figure 1, conductor 66, control relay 29, make con'-tacts 61 ofthe operated relay 21, make contacts 55 of the operated relay33, conductor 59 left, back contacts 60 of relay 22, both windings ofsimplex relay in parallel and out over both sides of the trunk by way ofthe repeating coil and back contacts .of relays 2| and 23 to negativebattery ,at the distant repeater, through the distant control relay 28gwhich operates to seize the distant repeater. and prepare it forvreceiving dial pulses. Control relay 29 in the calling repeater alsooperatesover this circuit.

Meanwhile, the operation of release relay 32 has busied the callingrepeater to the local switch train by grounding conductor 5 to theoutgoing selector E by way of make contacts of relay 32, back contacts44 of ,relay 30 and conductor 43. At its make contacts 68-relay 32 alsocloses a circuit over conductor 99 torelay 40, which operates todisconnect relay 39 so that the latter relay will not operate shouldanyone ring on lthe trunk at this time, through inadvertance orotherwise.

The operation of control relay 29 completes a circuit to relay 31 asfollows: ground on the busying conductors 5 and 43, conductor 69,conductor 10, make contacts 1|y of relay 29, conductor 12, breakcontacts 130i relay 38, and the winding of relay 31 to negative battery.Relay 31, whose functions are merely incidental or preparatory at thistime, operates over this circuit and locksto the busying lead by way ofmake contacts 14 and conductor 10. Relays 21, 29, 32, 33, 31 and 40 arenow operated, and the repeater is ready for dialing.

The distant switch train now returns dial tone over trunk conductors'land 2, said dial tone passing through the 'repeating coil by inductionand thence to the' calling'party by Way of line conductorsvi, 5|.and 4,passing freely like voice currents througlrcondensers |13 and |14 of therepeating' coil.y The calling party then proceeds to dialthe number ofthe Wantedparty in the distant exchange, thereby pulsing relay 21 overthe calling line loop: At each restorationof relay 21, its make contacts65 open vthe circuit to re1easerelay'32v momentarily, but relay 32 beingslowto release dueto having a copper sleeving lover its magnetic ironcore, remains operated; On the first restoration of relay 21 relay 25operates overv the Afollowing circuit: ground 'through back contacts 65'of relay 21, back contacts 15 of control relay 28, make kcontact-s 16of release relay 32, break contacts 11 of relay 3| and the winding ofrelay25 to negative battery. This-circuit is of course interrupted ateach re-operation of pulsing'relay 21 but relay 25 being made slow torelease, remains operated during each digit', restoring only betweendigits and afterthe last digit. When operated, relay 25 at itsmake'contacts 18 shunts winding |00 of the repeating coil to improve theloop dialing, and at its make contacts 19 shunts controlrelay 29 withthe non-inductive resistor 88 in order to improve the pulsing on thetrunk. This shunt may be traced as follows: left side of the winding ofrelay 29, resistor 80, make contacts 19 of relay 25, conductor 8|, backcontacts 82 of relay 36,'conductor 83 andthe right side of the windingof relay 29. v

'The pulsing circuit vto the trunk from line ground is now thereforethrough control relay 29 and resistor 80ini'p'ara'llel and thencethrough the interrupting contacts 61 of pulsing rela'y 21 and to thetrunk by' way of make contacts 55 of relay 33 and conductor 59. Thecircuit of controlrelay 29 is `opened momentarily at each release ofpulsing 4relay 21 but being made slow to release by the action of` theshunt, relay 29 remains operated. The control' relay similar to relay28, in the distant repeater, follows the pulses however and repeats themto `the distant switch train, which establishes vconnection to thecalled partysline. The distant exchange then rings the called stationautomatically or returns busy tone as required.' Onac'all to a busystation the busy tone like dial tone, comes back over trunk.- conductorsand 2, through therepeating coil to loop conductors 3 vand 4 and thenceto the calling party. f

Whenthe called station-answers, the distant repeater places ground onthe trunk in place of battery, restoring control relay 29 which now hasground on both sides of it." Control relay 29 on releasing `completes acircuitat its break contacts 86 to the battery reversing'relay 3|. Thiscircuit is as follows: holding ground from conductors 5 and 43,"makecontacts 46 of relay 33, conductor 84, break contacts 85 of relay 25,breakcontacts 86 of relay 29, conductor B1, breakcontacts 88 of 'relay36, conductor 89, back contacts 90 of relay 22, conductor 9|, makecontacts 92 of relay 31, conductor 93, and the winding of relay 3| tonegative battery. Relay 3| operates and at its contacts 48 and 54reverses the battery from relay 21 to the calling loop for supervisoryor other purposes as required. The connection is now complete with theltalking circuit'extending through the repeating coil and relay 21furnishing talking battery to the calling line. Relays 21, 3|, 32, 33,31 and 40 are operated and ground is on both ends of the trunk. At thetermination of the call, if the calling party disconnects first,Iholdingground through lthe selector E is removedfrom conductor 5, and

the callinglooptoupulsing relay-21 is opened. Relay `21 thereuponrestores, disconnecting line ground from the trunk at itsmake contacts61. Contacts 65 also openntheicircuit to release relay 32 "whichrestores. Relay 32-i'releasing, opens the circuit through its contacts68 Ito vrelay 40 which thereupon restores.` The release of relay 32 alsoopens make contacts 45..thereby removing busyingvground. from `conductorl 43, and..releasing relays 3|, 33iand `31..which werefheld operatedbythis ground after lthe'rernovalof4 holding ground fronrconductor5.4Relay 33 at its back contacts `55vre-e`onnects line battery-through theupperwinding offcontrol relay 28 to the trunk to signal'the distantrepeater. Control relay 28 operates `overithis circuit and re-operatesrelays 32 and 40 to hold the repeaterrbusy until the called`partyfclisconnects.-` Thescircuit to relay 32 isnow from ground at backcontacts 65 of pulsingrelay 21, make contacts lof control relay`28,fback contacts 94 .of relay 3|l`tore1ay 32 and negativer battery.yRelay 4U. opens `the circuit to relay 39 asbefore` and relay 32againconnects busying groundlto conductor 43; i When the distant called-partynow disconnects the `distant'repeater returns negative battery over thetrunk and since negative battery .is now again on both ends oflthetrunk, controllrelay `28 `re-l stores,releas`ing vrelays i32 vand 4U.The `repeater is now normal and ready for another call, in eitherdirection.-

` j 1 1 i Ifthe distantcalled party disconnectsrst, the distant repeaterplaces 'negative battery v'on the trunk; It will'be reniernberedthatduring conversation"relays21, v3|, 32133, 31 and 4l) were operatedandground was on both ends of the trunk through control relay 29.Negative battery from the distantend'of the'trunktlierefore causes theoperation of controlrela'yl29.v Control 'relay 29, upon operating, opensaty its break contacts 86, the circuit from'` holding ground throughmake contacts 46 .of relay`33, vconductor 84 vand break contacts 85 ofrelay 25 to the battery reversing relay 3|. Thereuponfrelay 3|' releasesand at its contacts 4B and 54 reverses the battery feed from relay 21tothe calling loo ,for release'supervision.

When the local-calling `party then disconnects, holdingA ground throughselectorE is removed from lconductor 5, and, the calling loop to relay21 is opened as before. lRelay '21 now restores,'and at its contacts 61disconnectsv control relay 29 and its associated `line ground from thetrunk, andrelay 29 releases. Contacts 65 of relay 21 'openthe circuit torelease'relay32 which also releases, and at its contacts 45 removesbusying groundfrom conductorll,v Thisu'nlocks relays 33 and 31 which nowrestore. Relay49also releases uponthe release of 32, due to the openingof contacts..68. ,The release of` relay33'` re-connects negative batteryto the trunk lthrough control relay by waygof back conetacij.s,515|iland 55 and conductor 59,l as before. Negative battery is now on bothends of the trunk, andv the repeater is againnormal and ready foranother call.

Repeater to repeater calls incoming conductors and 2,'back contacts 63and 64 of relay2l, back contacts 6| and 62 of relay 23, windingsk |02`and |03 of the repeating coil, both windings of the simplex relay 20 inopposition, backcontacts 6||Y of relay 22, conductor 59, back contacts55 of relay 33, conductor 96, back contacts 58 of relay 35, breakcontacts 51 of relay 38, conductor 95, upper winding of control relay28, conductor 56, rectifier disc 4| to negative line battery. f

Control relay 28 operating, closes a circuit to release relay 32 asfollows: back contacts 65 of theroutward pulsing relay 21, make contacts15 of Vrelay 28, bacl; contacts 94 of relay 30, and the winding of relay32 to negative battery. Relay 32 operates, busies the repeater as beforeby groundingl `conductors 43 and 5 through its make contacts45 and backcontacts 44 of relay 30, and at its make contacts` 68 closes a circuitto relay 40 which valso operatesto out off relay 39 and prevent thelatter from acting in case a waystation should inadvertently ring on thetrunk at this timex4 The groundingA Aof conductor 43 also energizes theupper winding' of relay 35, but this relay will not operate over itsupper winding alone. Nor does switching relay 33 operate, since itscircuit is opened at contacts 45 of relay 32 at the same time thatground is placed on' conductor 43 by these contacts.

kThe `operation of control relay 28, at contacts |05 also closes theloop circuit of the incoming selector Dtoseize this selector. Thiscircuit may betraced as follows: positive line conductor l0,breakcontacts 41 of relay 33, conductor 5| left, winding ofthe repeatingcoil, conductor 59, lower winding of `relay 35, resistor 91, conductor93;# back contacts 53 of relay 33, conductor 52, windingflillv of therepeating coil, conductor 3, make contacts |95 `of control relay 28,break contacts |06 of relayl30 and back to the selector over thenegative line conductor 9. The incoming` selector is seized thereby andmade ready to receive dial pulses, `returning dial tone to the distantexchange. This dial tone circuit is as follows: line conductor I0, breakcontacts 41 of relay 33, conductor 5|, `wir'iding |00, condenser |14and-winding ||l| of the repeating coil, conductor 3, make contacts |95of relay 28, break contacts |06-'of relay 30, and line conductor 9 lbackto the selector'.` Atthe repeating vcoil it is induced into trunkconductors I" andI 2 and thence to the distant repeater and to thecalling party. Both windings of the pole 'changer' relay 35 are nowenergized, butin opposition,y so that this relay still remains normal.Only relays 28, 32 and 40 are operated at this time.' l l When'dialingbegins at the distant exchange the control-and-inward-pulsing relay 28follows the ground pulses on the trunk, and repeats them through itscontacts |95 to the incoming selector and the local switch train whichrespond and make connectionto and ring, the called station. Relay ,25operates on the first pulse of each digit as before from ground throughback contacts 65 of ;the unoperated relay 21, and closes contacts 18 toimprove the loop pulsing. The interruptions in the ,circuit of relay 25are now from the break contacts 15 ofgrelay 28, but this relay asbefore, releases only between digits and shortly after the last digit. y

When the local called line answers, the local switch train reversesbattery yto the previously tracedwloop, circuit, I.which reverses the`current in the lower winding of relay 35 which is a part cedingparagraph will cause the operation of reof this circuit. The polaritiesof the two windings of this relay are now aiding each other, and relayA.35 operates to ground the trunk as'a supervisory signal to the distantrepeater. Relay 29 in.the-distant repeater thereuponrestores and causesreversal of battery' to the calling loop in tliedistant exchange in themannerexplained for an outgoing call, through the operation of thedistant relay 3|. This provides answer supervision, in cases where anoperator is involved in thezcall.

Relay 35, at its contacts |01, connects ground to the .lower winding ofcontrol relay 28 by way of conductor |08 and .break contacts |09 ofrelay 29,.to prevent relay 28 from releasing when its upper'or serieswindingis opened. Relay 35 also, at its contacts 58, disconnectsnegative line battery through control relay 28 from the trunk andconnects line ground through control relay 29 in its stead as stated.Control relay 29 does not operatel at this time however, since ground isnow again on both ends of the trunk. The connection is nowcomplete, withtalking battery furnishedto the called party from the local switchtrain. Repeater relays 28, 32, 35 and 40. are op-4 erated, and ground is.on both ends of the trunk.

If. the called station is found busy, of course the local switch trainwill not ring, but will return busy tone to the calling party instead.This busy tone reaches the repeating coil in the same manner Vas dialtone, by way ofline conductors 9 and l from theincoming selector,contacts 41, |06 and and'conductors 3 and 5|, and is similarly passedthrough the repeating coil by induction tothe .trunk conductors and 2,and thence through the .distant repeating coil to the calling line..`Thev .calling party on hearing the busy tone will disconnect and attemptthe call later.v

.At the termination of-the call, ifthe calling partywdisconnects iirst,the distant repeater, as previously explained for an `outgoing call,partly releases,` restoring its switching relay 33, which at itsoontacts55 re-connects negative line bate tery through relay 28 to the trunk inp lace Of.

lilleground` U Control relay `29 atv the called repeater now operatesfrorrrthe negative line battery on the trunk, andat `its contacts 1|completes a. circuit tc 1, relay'.1I as follows: ground from conductor43conductor 69, conductor 10, make contacts 1| f of relay 29, conductor12, break'contacts 13 of relayq 38, and the winding or relay 31 tonegativey battery. Relay 31 operates and locks, and at its`contacts"l|3opens the incomplete'circuit to relay' 38 to prevent the prematureoperation of this'relay. Control relay 29 also,` at its break contacts|09 opens the holding circuit to the lower winding of control relay 28,which then releases] "Control relay 28, at its contacts |05, opensthe"called line loop to release the local switch train, and at its contactsopens the circuit to release relay 32 which restores. Relay 32 atitscontacts `68 opens the circuit-'oi relay 40 and at its contacts 45opens the circuit to the upper winding of relay 35, and both of theserelays also `restore.` Relay 35 at its contacts -58 disconnects controlrelay 29 and line ground from theA trunk and re-connects line batterythroughA control relay'28 in its stead. Relay 29 releasesand therepeater is once again normal withnega-A tive battery on both ends ofthe trunk.

ifithe local switch ltrainl is arranged for last party release however,`it will not release, but.

willfmaintain ground on.'conductor I Iiyand upon the releasefof relay 32as .explained 1n the prelay 38 by way of break contacts ||0 of relay 25,break contacts of relay 32, conductor ||2, break contacts ||3 of relay31, and winding of relay 38 to negative battery. Relay 38, at its breakcontacts 51 disconnects control relay 28 from the trunk, and at its makecontacts 4 connects line ground through control relay 29 to the trunk toseize and hold the distant repeater. The circuit is thus held busy tofurther calls until the called station has also disconnected, When thisoccurs, ground is removed from conductor and relay 38 restores. Relay 38at its contacts ||4 disconnects line ground through control relay 29from the trunk and at its contacts 51 re-connects line battery throughcontrol relay 28. Relay 29 releases and the repeater is again normalwith negative battery on both ends of the trunk.

If the local called party disconnects first, it being remembered thatrelays 28, 32, and 40 were operated during conversation, and that lineground through control relay 29 was connected to ,both ends of the.trunk, the local switch train reverses battery over the called line loopthrough the lower winding of relay 35. Since the polarities of the twowindings of relay 35 are now opposed to each other this relay restores.Relay 35 at its pole changing contacts 58 disconnects control relay' 29and line ground from the trunk, and connects line battery throughcontrol relay 28 to the trunk in its stead, to give release supervisionto the distant exchange. Relay 35 also at its contacts |01 opens thecircuit to the lower winding of control relay 28. which is however nowheld operated over the trunk. Relays 28, 32 and 4,0 are therefore stilloperated'.

When now the distant calling party disconnects, the distant repeaterputs negative battery on the trunk causing the release of vcontrol relay28 which at its contacts 15 causes, the release of relay 32 and at itscontacts |05 opens the called line loop through relay 35, releasing thelocal switch train. Relay 32 at its contacts 45 opens the circuit to theupper winding ofA relay 35 which is already released however, and at itscontacts 68 relay 32 opens the circuit of relay 40 which restores, Therepeater is again normal and ready for a new call.

Repeater to waystation calls.`

Under this heading, the action of both repeaters on an automatic call toa waystation will be considered, 'with the operation ofv therepeater atthe originating exchange being considered first, and' the mannerl of thebusying ofthe distant repeater last. On such a call1 the ilrst part ofthe number dialed by the local calling party will cause an outgoingselector such as E to raise its wipers to the code ringing.level hereshown as level 8, and to hunt and seize an idle repeater such as shown.The line wipers of the selector will be thereby connected to the talkingconductors 6 and 1 of the repeater, and the'busying wiper to the busyingconductor 8, It will be noted that the negative line conductor 8 fromthis levelv passes through the upper winding of a pole changer relay 36and thence toA the repeating co1 The outgoing selector, on connectingthrough to. .the repeater, passes ground forwardover the busying wiperto conductors .8. and 43,. causing. the operation of switching relay 33as. for a through call, by way of break contacts 4.4 and of relays .30and` 32. This same ground also. energizesA the upper winding of relay35, but :thisis vwithout eifect and relay remains normal. ,i if iSwitching relay 33 operating, locks .directl to conductor 43 atfcontacts46at contacts. 55 dise connects control: relayi28 and negative" batteryfrom thetrunk, at contacts 41 disconnects the incoming selector; fromthe repeater, and at contacts 49gand 53 connects pulsing relay 21'y tothe local calling' loop over thev following' circuit: ground through thelower winding of relay V21, backcontacts 48 `of relay 3|,#makev contacts49 of relay 33,Y conductor left,winding |00 of the repeating coil,conductor 5|, the loopconduc'tor 1, through the selectorlbank and thecalling loop and back to the selector bank and loop conductor 6, theupperwinding of pole changer relay 36,

conductor 3lleft,`winding |0| of the repeating coil, conductor 52, makecontacts53 of relay 33, back contacts 54 ofrelay 3|, and through theupper winding of relay 21 to negative battery.

break contactsff||5 ofrelay 26, conductor H6,

make contacts ||1 of relay36, and the' lower winding ofirelay 36 `tonegativebattery. Both windings Iof relay 36'are now aiding and thisrelay remains operated.` Relay 36 at' its make contacts f ||8 alsoprepares the"pickup'circui t which is associated with the ringingequipment, and at make `contacts 02 c'onnects'line-ground throughcontrol relay 29to`the trunk to seize and busy the distant repeater.This circuit isfrom line `ground and conductor v65,th`rough relay 2S,conductor 83, make contacts 32 of relay 36, conductor |23, make contactsof relay" 33, conductor 59, back contacts of relay 22, and thencetorelay 20 and out over the simplex. jContactsZ of relay 36 also shuntthe pulsing contacts ofrelayfZl. in order to prevent pulsing kon thetrunk. "This shunt may betraced as "follows: uppercontact 61, conductor83, make'` contacts'82' of relay 36, conductor |23, and backto`lower`contact'-61. Relay 23 operates, and at its con'tac'ts'1lAconipletes a circuit to relay 31 `\ivhich4 operatesfand locksU toconductor V43. Finally, at its contacts |24, relay` 36 prepares apulsing circuit tofthe motormagnet |26 ofthe code selectorsu'ZitchB.` i

Pulsing relay 21 .upon operating establishes, atits make contacts 61,asecond circuit forline ground to thetrunk through make contacts 55 ofrelay 33, at itsmake contacts closes a direct circuit torelease relay 32which operates and at contacts '16 further prepares the pulsing circuitto the code selectorswitch. Relay 32l also operates relay 40 as beforeto disconnect relayv-39 and prevent operation of the latter relay shoulda waystation happen to ring on the trunk `at `this time, and at itscontacts 45,connects,repeater busying ground to conductor 43 asbefore,1so that conductor 43 is nowv grounded both from `the re.- peaterand from the outgoing selector. i

Relay 31 upon` operating, at its make contacts |21 shunts the serieswinding of relay 36 in rorder to improve the pulsing on the localloop,at its ymake contacts 92prepares the circuit to battery reversing relay3|, and at make contacts |28 prepares a locking circuit to the pick uprelay 34. Relays 21, 29, 32, 3'3, 36, 31, and 40 are now operated, andthe vrepeater is' ready `for dialing When the calling partydialsthenalfdigit of thewaystation number, relay 21 1will followy thescription of the drawings.

dial pulses., The outward pulsing contacts 61 of relay 21 'are withouteffect however, due vto being shunted by make contacts 82 of relay 36,and there is no pulsing on the trunk. Pulsing to the code selectorswitch does occur however, over the following circuit: ground throughback contacts 65 of relay 21, back contacts 15 Aof relay 28, makecontacts 16'of relay 32, conductor |63, make contacts |24 of relay 36,conductor |25 and the winding of motor magnet |26 to negative battery.vThis causes the code selector switch to step one step ateach release ofrelay 21 and position its wipers in accordance with the digit dialed.Relay 25 operates onthe rst pulse in parallel with the foregoingcircuit, through break contacts 11 of relay 3|, and at contacts 1Bshunts winding l|06 of the repeater to improve the pulsing on the loop.Break contacts 85 of this relay open a circuit tothe off normal springs|30 of the code selector switch preparatory to the closing of thesesprings which occurs as the switch wipers move away from their normalposition on the first step. Relay 25 remains operated during thepulsing.

Relay 25 on releasing shortly after the last pulse of the digit, causesthe operation of ring start relay 24 over the following circuit: groundfrom conductor 43, -through make contacts 46 of relay 33,"conductor 84,break contacts 85 of relay 25, conductor |23, code selector off normalsprings |30,l and the winding of relay 24 to negative battery. Relay 24upon operating locks to the ground on conductor 84v at make `contacts|32 independentlyofthe aforementioned break contacts 85 of relay 25, andat its make contacts |33 connects ground to the ringing machine startconductor |34 to start the ringing machine, and the automatic codeinterrupter C. Relay 24 also, at its make contacts |2| connects the ringpick up relay. 34' to the pick up lead |15 which is grounded momentarilyby the. code ringing equipment at the end of each coding. cyclev toinsure that ringing will not start in theV middle of a code, and atcontacts |391prepares a release circuit to the code selector switch.

The code ringing equipment now starts vand connects the' alternatingcurrent pulses :of the various ringing codes to the contacts of the codeselector switch, as previously covered in the de- When now, the coderinging equipment grounds the pick up lead |15, relay 34 operates overthe following circuit: ground on conductor |15, through make contactsIIS of relay 36, back contacts I6 of relay 34, conductor |20, makecontacts |2| of relay 24, conductor |22, and the winding of relay 34 tonegative' battery. Relay 34 at its make before break contacts v| I9disconnects the pick up lead, and locks to ground at makecontacts |28 ofvrelay 31 by way of conductor |35, back contacts |36 of relay 26, andconductor |31. Relay 34at its contacts |5| also prepares a circuitl overconductor |52 lto the alternating current relay 2| of Figure 1.

The grounded alternating current pulsesof the ringingY code of thecalled waystation, now pass from the selected bank contact of the codeselector switch to the switch wiper and conductor |46, through thecondenser |49, conductor |50, make contacts I5| of relay 34, conductor|52, and the` winding of relay 2| to grounch Relay 2| follows the codedpulses and at its makercontacts 63 and 64 repeats them to the trunk tosignal the waystations withv insulated ringing generator via conductors|68 and |69, and thence direct to the trunk conductors and 2.

Each operation of ringing relay 2| also causes the operation of drainrelay 23 from ground at make contacts |65. Each operation of relay 23 inturn disconnects the repeating coil from the trunk circuit at backcontacts -6| and 62, and at make contacts 6| and 62 connects resistor|10 to this circuit. Since this relay is made slightly slow to releaseby a copper sleeve on the core, it remains operated momentarily aftereach release of relay 2| in order to permit the trunk line to drainthrough resistor |10 after each pulse of ringing current. Condenser |1|and resistor |12, bridging back contacts 63 and 6| of relays 2| and 23,provide a path for ring back tone to line ground through winding |02 ofthe repeating coil during code ringing, which is then passed byinduction through the repeating coil to the calling loop.

On the first operation of ringing relay 2|, make contacts |66 of thisrelay complete a circuit to relay 22 as follows: ground on the busyingconductor 43, conductor 69, conductor 10, make contacts |66 of relay 2|,back contacts of the make before break springs |61 of relay 22, and thewinding of relay 22 to negative battery. Relay 22 operates over thiscir-cuit and locks direct to conductor 10 and busying ground throughmake before break springs |61 which at the same time disconnect the pullup circuit through contacts |66. Relay 22 at its back contacts 60disconnects control relay 29 and line ground from the trunk circuit, andat make contacts60 connects line battery to this circuit throughauxiliary control relay 26, by way of conductor |53. When thereforerelays 2| and 23 restore after each code pulse, relay 26 and linebattery are connected through to the trunk. Since however the distantrepeater also has battery on the trunk, relay 26 does nothing at thistime.

With reference to the trunk and waystation diagram of Figure 4, it willbe obvious that the ringing pulses on the trunk will ring all of thewaystation bells in multiple. The waystation party whose code is beingrung, answers by removing his receiver and tripping the hook latch topermit full operation of the hook switch. This closes contacts 206 and201, grounding both sides of the trunk, and also connecting thewaystation talking circuits across the trunk.

Returning now to the repeater at the calling exchange, the ground on thetrunk from the answering waystation causes the operation of theauxiliary control relay 26, on the next succeeding de-energization ofrelays 2| and 23, over the following circuit: ground from trunkconductors and 2, back contacts 63 and 64 of relay 2|, back contacts 6|and 62 of relay 23, windings |02 and |03 of the repeating coil, bothwindings of relay 20, make contacts 60 of the locked up relay 22,conductor |53, winding of relay 26, conductor 56, and through therectifier disc 4| to negative line battery.

g Auxiliary control relay 26, upon operating, at its break contacts ||5opens the locking circuit to relay 36, and at its back contacts |36opens the locking circuit to relay 34, causing the releaseof both ofthese relays. Relay 26 at its make contacts |36 closes a circuit tobattery reversing relay 3| as follows: lground through make contacts |28of the locked up relay 31, conductor |35, make contacts |36 of relay 26,conductor |58,

make contacts 90 of the locked up relay 22, conductor 9|, make contacts92 of relay 31, and conductor 93 to the winding of relay 3| and negativebattery. l

Battery reversing relay 3| operates over this circuit and at its makebefore break contacts 48 and 54 reverses battery to the calling loop asbcfore to give answer supervision. Relay 3|v at its make contacts |4|also completes the release circuit of the code .selecting switch asfollows: ground at make contacts |38 of the locked up relay 22, makecontacts |39 of the operated ring start relay 24, conductor |40, makecontacts |4| of relay 3|, conductor |42, code switch off normal springs|43 and the Winding of the release magnet |44 to negative battery. Therelease magnet operates to disengage the ratchet, and the switchrestores to normal by spring tension. Theloff normal springs then open,disconnecting the release magnet and relay 24, which both restore. Relay24 releasing, stops the code ringing equipment by opening contacts |33and further opens the code switch release circuit at contacts |38. Theconnection is now complete and the repeater is ready for conversation,with relays 22, 26, 21, 3|, 32, 33, 31 and 40 operated.

Upon termination of the conversation, ifthe local calling partydisconnects first,.the calling loop is opened to pulsing relay 21 andthis relay restores and releases relay 32, Relay 32 in turn releases 40and removes busying ground from conductor 43. Since holding ground hasalso been removed from this lead by the switch train, relays 22, 33 and31 which were locked to this conductor,.also restore. Relay 3| alsorestores, due to the opening of its circuit at contacts 92 of relay 31.Relay 22 uponv releasing, disconnects line battery through relay 26 fromthe trunk at contacts 60, causing the releaseof relay 26, and reconnectsline battery through relay 28 to the trunk in its stead. Relay 28 nowoperates from waystation ground and causes relays 32 and 40 tore-operate to hold the repeater busy until the waystation disconnects.

When the waystation disconnects in turn, it removes ground from thetrunk. Control relay 28 now encounters battery on the trunk from the ydistant repeater and is shunted down. Control Irelay 28 releasing,causes the release of relays 32 and 40, and restores the repeater to itsnormal condition.

If thewaystation disconnects first, the removal of ground from the trunkat the waystation permits negative line battery from the distantrepeater to shunt down relay 2B which restores. Relay 26 at its contacts|36 opens the circuit of relay 3| which was held, it will be recalled,from ground at make contacts |28 of relay 31. Relay 3| thereuponrestores, and reverses the polarity of the calling loop at its contacts48 and 54 to give disconnect supervision as previously described.

Wlien the local calling party then disconnects, relay 21 restores 0n theopening of the loop circuit and releases relay 32 as before. Relay 32causes the release of relays 22, 33, 31 and 40. Relay 22 disconnectsrelay 26 from the trunk and re-connects relay 28 thereto in its place.The repeater' is again normal and ready for another call, and negativeline battery is again'on both ends of the trunk through the controlrelay 26 in each repeater.

` The busying of the distant repeater, on a repeater towaystation call,takes place as follows. Upon the original seizure of the callingrepeater, it will be remembered, its relay 36 operated to connect lineground from relay 29 to the trunk,

'release-nature of relay 32;-22 w v f i Via make contacts 82, thiscircuit being from line ground through relay 29, conductor 83, makecontacts 82 of relay 36conduct-or |23, make contacts 55 of relay 33,conductor 59, and thenceto the trunk through back .contacts 60 of relay22.

Sincethese same contacts 82 of relay 36 also shunt the outwardpulsingcontacts 61 vof relay 21, as previously explained, this is asolid ground,

.and is not .aiected by the dialing of the final or code .selecting-:digit of .the4 .waystation number. At the distantrepeater, this groundVcauses the :operationzof the distant control; relay 28; and theresultant operationgof associated relays 32 and l|10.Relay.32groundsconductor .43vfrom-1nake i contacts .45to busy the.-repeater., while relay. 28 "at contacts .|05 .completesthe loopcircuit`to the incoming selector D..` `Thedistant incoming 4sei lector isseized .momentarily overthiscircuit, and

returns -dialatone inthe usual manner. When the calling lrepeater`starts "ringing however, it re- .i moves Vline yground from'theL trunkcausing the `distant control relay.28f.toirelease again.. The i distantcontrol relay. -28 at its, contacts I 05, .opens the lloop` circuitltothe' distant incoming selector whichV releases, and .stops thedialtone.,` The reV leaseofrelay 28I also icauseszthe release of relays32 and 40 after a slight delay, due to the slow to f Meanwhileftheringing-current placed 'on the trunkby the calling repeater, in additionto ringing-the bells'at the waystations'also causes the Aoperation of-the distant` alternating i current sim- `plex relay 20, the-cur-rent=passing through` both windings of thisl'relay'infseriesandthusto the other trunk conductoryand'back to they source.

In-series, thewindings of relay'i20 are polarized to aidleach other;which perm-its'itto respond to relay'2l! in they distant repeaterclosesafv 'circuitstethe distant vibrating reedrelay Iilifrom groundatfmake contacts |45 `oi` relay 'overconductor' |45, through break`39tol'negative*battery Relay 39' operates over' this `circuit"andoperates relayv from'make contacts f' |59 *over 'conductor |60.frnajdefslow to release,` for-'reasons lwhich will be vmade"` 'clear 'inthe Anext paragraph, by means Aof a heavy'` opper-slugf'placed' overthel core, at the varmature"end oi? the Vrelay. This same slug also,tendsto makethe relayfslightly slow to operate;

which' assuresgoodinagnetic saturation'of the corev before operation'.-f The slug is indicated on thedra'wingsat theiipper end of the relay.Relay "30 lupon operating, `locks 'through its make contactsl'ezandlconductorrel tov'ground at the second locking Acircuit "for itself"at make 'contacts 94; andL at lmake contacts 44 place'swground on`conductor 43' to I'naintain :the busy-on the rejpe'ater; *Finally relay30 Iat Vbreak'contacts |06 1 opens the circuit-to the incoming` selectorD at 'a second point. `The distantrepeater lis thus held busy byiitsoperated relay 30,* b 'up any othereiluipmentiV -v l f Inthe" pauses*between theI rings of lthe code, i Irelays -20 andI 39 'ofthevl distantrepeater restore, f butj relayf 39` at its'springs il 59, ysets iupfai`o scillatingmontact w'hiclif holds slowuelay30 'operated daring theseintervaisn Relays 39 nasa-weighted "vibrating reed farin'at'ure",` whichi onli operationi t without tying Relay 430 IisI strikes against thecore of the coil and makes a firm contact from ground through itself tothe associated make springs |59. Upon release however, `the reedvibrates rapidly for a considerable period, .and thus maintains `anonds.

When the waystation answers and grounds the trunk to cutoff the ring atthe calling repeater, control relay 28 at the distant repeaterre-operates from this ground, and closes the upper locking circuit ofrelay 30 to ground at back contacts v65 of relay 21, through makecontacts l5 of relay .28 and make' contacts 94 of relay 30. Relay 30 nowremains operated after relay 39 has finally come to rest following itsfinal release, upon the cessation of ringing. Relay l32 does notre-operate from relay 28 at this time because of the open `back contacts94pm relay 30. When the connection is released, and ground is removedfrom the trunk, the stated distant'relays 28 and 30 restore, and againfree the distant repeater.

waystation to waystation calls Waystations on the trunk call one anotherby ringing the code of the wanted station with the Yhand generator.` Tomake such a call, referring again to Figure 4, the calling party removeshis 'receiver from the hook, thereby closing hook trunk at its springs2| I, upon being operated, and` at the same time to disconnect theringer momentarily. I

' The ringing current on the trunk, in addition to ringing the bells ofthe other waystations, also operates the simplex relays 20 in therepeaters at each end of "the trunk, passing through both windingsoffeach relay in series.

`Each relay 20 causes the operation of the associated vibrating reedrelay 39 over conductor |46, and each relay 39 causes the operation ofits associated relay 30. The relays 30 at contacts 44 ground the 43conductors to busy both repeaters. This prevents seizure of eitherrepeater from the exchange end, and thus prevents interference with thewaystation call. The relays 30 also at break contacts |06 open theincomplete incoming iductors and -2 of the trunk in parallel.

signals are kept up until `the called party answers.

The called waystation answers by removing the receiver and tripping thehook latch to permit completeoperation of the hook switch.v This gclosescontacts-.201 of Figure 4, which connect ground to the center point ofthe ringer 203, through dial impulse springs 204, and so to con- 'I'hissaid first relay, thereby to operate and control said control relays andsaid' repeaters yover said control circuit, and unidirectional currentconducting devices in the circuitv of said ungrounded battery terminalsto prevent -false operation of said control relays over said controlcircuit due to differences of potentialat the two exchanges during thetimes that eachend of said control circuit is connected'to theungrounded terminal of the separate battery atfeach exchange.

5. In a telephone system, two exchanges, a trunk` line connecting saidexchanges, altwo way impulse repeater at leach end of said trunk line, abattery-at each exchange, grounded and ungrounded terminals for saidbatteries, a two way ground return 'control circuitl superimposed onbothv conductors of said trunk line in parallel, control relays at eachrepeater including a, iirst relay connected to the ungrounded terminalof the batteryand a second relay connected to the grounded terminal ofthe battery', said rst relays being normally connected also totherespec- `tive ends of said control circuit, means at each vtimes whenboth ends `of said'control circuit are connected Itocorrespondinglterminals of the battery at each-exchange. 1 f

6.1Ina telephone system, two exchanges, simplex trunk linesconnectingsaid exchanges, separate sources of line current at each exchange, twoWay ground return control circuits superimposed onsaid trunk lines, apluralityof control .relays associated with eachend of each saidcontrol'circuitpsaid control circuits and said relays being connected tosaid'sources of line current and `controlled over bothsides ofthelassooiated trunk line by reversals of line polarity and circuitinterruptions at either end of thev control circuit,

and unidirectionalcurrent Vconducting devices ,1

associated with said control circuits to prevent line current flow overany of saidcircuits and resultant faulty-operation of said 4circuit`when both ends of said circuit 'are connected to equivalent polaritiesat the` respective-sources of line cur.rent.--y i '7. In a telephone`system two exchanges, simplex trunk lines connectingsaid exchangesseparate sources of' line current `at xeachiv -exchange, two way groundreturn control circuits superimposed on said trunk linesgsaid controlcircuits being connected to said sources of line current" and operableover yboth sides ofthe associated trunkline in parallel, two way impulserepeaters at the ends oi 'each of said trunk lines, a plurality-ofseries vrelays associated-with'each of said'repeaters and with the endsof said control Vcircuits, said -relays being operable `by reversalsofline-polarity and circuit interruptions at either end ofthe controlcircuit, means at each repeater for veffecting .said reversals-and saidinterruptions and-controllingx-said relays and said repeaters in `theprocess oi vmaking -and releasing icalls, and' unidirectionall currentconducting `devices associated with saidzcontrol1 cir- `cuits to preventline current llow over any of said circuits and' resultant faultyoperation oi such circuit, while both endsof such circuit are connectedto corresponding line polarities at each exchange.

8. In'la telephone system, two exchanges, a

trunk line connecting said exchanges, a separate source of 'current ateach exchange, positive and negative terminals for each-of said Asourcesoi current,` a two way ground return vcontrol circuit superimposed onone conductor roiusaid trunk line, a relay at each exchange, a windingon each said relay connected in series with said control circuit andnormally connected to the positive terminal of the separate source oicurrent at each exchange, means at each .exchange for connectingthenegative terminal ol said source to saidrelay in place of saidpositive terminal, and for re-connecting the positive terminal, therebyto operate and control said relays over said control circuit andunidirectional current conducting devices in the circuit of saidnormallyconnected terminals at each exchange to prevent current flowover the control circuit and resultant false operation of said relaysdue to differences of `potential at the two exchanges during the timesthat both ends of saidv control circuitare connected to the positiveterminals of saidseparate sources of current. I

9, In a telephone system,. two exchanges, a trunk line connecting saidexchanges, a separate source of current at each exchange,'positive,andnegative terminals/for each of said` sources, a two way groundv'retuincontrol circuit superimposed'on one conductor of said trunk line, arelay at each exchange, a winding on each of said relaysconnected inseries with said control circuit and normally connected to `the positiveterminal of the separate source of current at each exchange, meansateach exchange for connecting the negative terminal of said source tosaid relay in place of said positive terminal, and yfor re-connectingthe positive terminal, thereby tooperate and control said relays oversaid control circuit, and unidirectional current conducting devices inthe circuit of each of said terminals at both exchanges to preventfaulty operation of said relays due to diierences of potentialat the twoexchanges during the times that both ends of said control circuit areconnected to corresponding terminals of said separate sources ofcurrent.

l0. Ina telephone system, two exchanges, a trunk line `connecting saidexchanges, `a separate source of current `at each exchange, lineterminals for each of said sources of current, a twoway ground returncontrol circuit superimposed on one conductor of said trunk line, acontrol relay and associated equipment at each exchange, a winding oneach said control relay each said winding being connected on one side tosaid control circuit and on the other side being normally connected tovline terminals of like polarityat each exchange, means at each exchangefor connecting the other line terminal to said winding in place of saidnormally connected terminal, andfor re-connecting the normally connectedterminal, said relays being operated and. controlled over said circuitin response to saidchanges in terminal connections toopervate saidassociated equipment, and unidirectional current yconducting devicesinthe circuit of said normally connected line terminals to prevent falseoperation of said'relays over said control circuit due to differencesof'. potential at-the two at Veach end of said control circuit foreffecting said reversals and removals of polarity to operate andcontrolsaid relays and said associated equipment, and unidirectionalcurrent conducting devices associated'with said control circuit toprevent lmis-ffunctioning'of said control Ycircuit due todiierences ofpotential between the two ends ofthe circuitduring the times that bothends of said circuit are connected to the same 'respeccurrent. 3

` 18.1I`nfa telephone system, two exchanges, a two-way impulse repeaterat each exchange, a trunk line connectedto said repeaters, waystationsinsaid trunk line, means in each repeater for seizing the distant repeaterand repeating dial impulses to thev distant repeater over said trunkline, means in each repeater `for calling a given waystation and at theSametime busying the distantrepeater, means at each waystation forseizing and dialing through either repeater and at the same time busyingthe other repeater, andv means at each waystation for calling anotherwaystation and at the same time busying both repeaters.

19. In a telephone system, two exchanges, a two way impulserepeater ateach exchange, a trunk line connected to said repeaters, telephonewaystations in said trunk line, a plurality of points of access to saidrepeaters in each exchange comprising a nrst point of access used onthrough calls tothe distant exchange and a second point ofaccess used oncalls towaystations, means in each repeater controlled from the firstpoint of access for seizing the distant repeater and repeating dialimpulses to the distant repeater over said `trunk line on through calls,and means in each'.` repeater controlled from the second point tivesides or polarities of the separate sources of of access for coderinging on the trunk to signal the waystations and at the same timepreventing dial impulses from reaching the trunk on calls toawaystation. l

2,0.` .In va telephone system, two exchanges, a two way impulse repeaterat each exchange, a trunk line connected to said repeaters, telephonewaystations in said trunk line, a plurality of points of access to saidrepeaters in each exchange comprising a rst point of access reserved forthrough calls to the distant exchange and a second point of accessreserved for calls to waystations, means in each repeater controlledfrom the first point of access for seizing the distant repeater andrepeating dial impulses to the dis` tant' repeater over said trunk lineon through calls, means in each repeater controlled from the secondpoint of access for impressing code ringing signals on the trunk tosignal the waystation, means at said waystations for grounding the trunkwhen answering, and means in said repeaters responsive .to saidgrounding of the trunk by the waystation for automatically disconnectingsaid code ringing -signals from the trunk.

21. In a telephone system, two automatic exchanges, a two way impulserepeater at each exchange, said repeaters `being accessible overdiilerent paths on outgoing calls, said paths depending on the -natureof the call and the number dialed, a trunk line interconnecting saidrepeaters, telephone waystations in said trunk line,

means in'said repeaters for repeating dial `impulses over said trunkline to the distant repeater when seized over one pathl reserved forthrough` calls, `means in said repeaters for `placing coderingingqsignals on the trunk tosignalsaid waystations when seized over asecond path reserved for calls to waystations, means including saidringing signals for busying the distant repeater on such a ca11,means atsaid waystations for grounding the trunk when answering, means inchanges, a two way impulse repeater at each exchange, a code selectorswitch responsive to dial impulses in each repeater, different paths ofae` cess for said repeaters for outgoing calls, the path selected on anygiven call depending on the l nature of the call and the number dialed,a trunk line interconnecting said repeaters, telephone waystations insaid trunk line, means in said repeaters for repeating dial impulsesover said trunk line to the distant repeater when seized over one pathreserved for through calls, means in said repeaters including `said codeselector switch for placing code ringing signals on the trunk to signalsaid waystations and at the same time preventing the repetition of dialpulses to the trunk when seized over a second lpath reserved for callsto waystations, means at said waystations for grounding the trunk whenanswering, means in said repeaters responsive to said grounding of thetrunk` for cutting off the ring at the calling repeater, means forbusying both repeaters during the establishment of a call, meansresponsive to the grounding of the trunk by the waystation for keepingboth repeaters busy untilthe waystation disconnects, and means at saidwaystations tor automatically removing said ground from the trunk upondisconnecting, thereby to permit the release of said repeaters,

23. In a telephone system, two automatic exchanges, a two way impulserepeater at each exchange, different paths of access to said repeatersfor outgoing calls, incoming equipment associated with said repeaters ateach exchange, said incoming equipment being normally seized on anincoming call by ground on the trunk, a simplex 'trunk line connectingsaid repeaters, telephone waystations in said trunk line, means in saidrepeaters for repeating dial impulses over said trunk line to thedistant repeater when seized over one path utilized for through calls,means in said repeaters for placing code ringing signals on the trunk tosignalthe waystations when seized over a second path utilized for callsto waystations,

'means responsive to the initiation of such call to I keeping bothrepeaters busy until the waystation disconnects, and means at saidwaystations for automatically removing the ground from the trunk whendisconnecting, thereby to permit the release of -said repeaters.

24. In a telephone system, two automatic exchanges, an impulse repeaterat each of said ex changes, a, simplex trunk connecting said repeaters,telephone waystations in said trunk, means at said waystations formaking calls to either exchange by impulsing into either repeater'withground dial pulses over both conductors of thetrunk in parallel, meansin said repeaters responsive to said impulses for completingthe call,

means at said waystations for opening the trunk! in the direction of theother-repeater before dialing, means at said waystations for maintainingground on the trunk in both directions and over both conductors of thetrunk in parallel during such a call, means in said repeatersresponsiveto Said ground for maintaining both repeaters busy to othercalls until the waystation has `disconnected,` and said waystationground maintain-` ing meansremoving-.said ground and restoring the trunkto normal on disconnect, to permit-thev release [of said repeaters.

25. In-a telephone system two exchanges, a two-way impulse repeater atveach of said'exchanges,4 a trunk line connecting said repeaters,magneto telephone waystations in said trunk line, means at saidwaystations comprising a hand generator for calling another waystationby code ringing on the trunk, means at said waystations for groundingthe trunk in both directions from both waystations after the calledwaystation'has answered, means in said repeaters responsive-to thecoderinging on-the trunk for busying both repeaters, means in saidrepeaters :responsive to the ground on thetrunk for holding bothrepeaters busy until both waystations have disconnected, and saidwaystation grounding means removing said ground from thetrunk ondisconnect to release said repeaters. l l

26. In a telephone system, two automatic exchanges, i two-Way impulserepeater at each exchange, incoming equipment associated with saidrepeaters at each exchange, a trunk linefconnecting said repeaters,magneto telephone waystations in said trunk line, means at saidwaystations comprising a hand generator for calling another waystationby code ringing on the trunk, means at said waystations for groundingthe trunk in both directions from both waystations after the.

called waystation has answered, means in said repeaters responsive tothe code ringing on the trunk for busying both repeaters and at the sametime preventing seizure of the associated incoming equipment, means insaid repeaters responsive to the subsequent grounding of the trunk bythe waystations to maintain this busy on both repeat-l ers until bothwaystations have disconnected, andv said waystation grounding meansremoving said ground from the trunk on disconnecting, to release saidrepeaters.- v

27. In a telephone system,two automatic exchanges, a separate battery ateach exchange, a two way impulsefrepeater at each exchange, a trunk lineconnecting said repeaters, a two Way ground return control circuitsuperimposed on both conductors of said trunk line, the ends of saidcontrol` circuit being normally connected ,tol

peaters including said-code selector switch for placing code.ringingsignalsy orrthe trunk to signal said waystations and at theSametime preventing the repetitionof dial-.impulses to the, trunkinresponse to seizure over a second path reserved fory calls to aWaystation; means responsive to the initiation of a repeaterftowaystation callhfor lseizing and busying'the distant repeater andl theassociated incoming equipment, code ringing signal responsive means `insaid distant repeater operated by said ringing signals tofree theAdistant incoming equipment while maintaining the-busy-on said distantrepeater, means atsaid waystationsfor placing waystationy ground on Athetrunk'when answering-and'for `removing said ground from they trunk upondisconnecting atthe termination of the call, means -in thecallinglrepeater responsive to said playstation-ground for stopping the coderinging signals, busying means in said repeaters responsive to saidwaystation ground for maintaining the busy on both .repeaters until thewaystation hasdisconnected, and for permitting the release of saidrepeaters after the .waystationhas disconnected and removed waystationground from the trunk; dialing means at said waystations for making.calls to either exchange by impulsing into the selected repeater withwaystation ground pulses-over said trunk and said control circuit, meansin said selected. repeater responsive to .said impulses to complete-thecall, trunk splitting keys at said waystations for opening the trunk -inthe direction of the other repeater before rdialing and at the same timeconnecting waystationground to this end of the trunk to keep said otheryrepeaterrbusyfor the duration of thecall, waystationA ground being alsomaintained on the trunk in the Adirection of the called 4repeaterthrough saiddialing means to hold saidy called rrepeater after thecessation oidialing, means in said waystations responsive todisconnection by the waystationat the termination of the call forautomatically removing waystation ground from bothenvds of the trunk andrestoring the continuity of y saidtrunk, thereby tov permit thev releaseof said repeaters and their restoration to normaloperating condition; ahand generator at said waystations for calling another way station bycode ringing on the trunk, thegpreviously Astatedcode ringing signalresponsive means inv bothV repeaters being operated by said'lcode'ringing on `themtrunk to busy both repeaters and preventseizure ofthe associated incoming equipmentjin ,either exchange, said busycondition being maintained after the ringing period by Waystatio'nground` from both calling and answering waystations until bothwaystations havedisconnected; and means comprising a unidirectionalcurrent conducting device inthe ground return control circuit at ea'chexchange to prevent false operation of said control circuitand'sai'drepeaters due togrdifferences of battery potential at the-two exchagesWhile ther system is at rest.

28. In a telephone system,`"a first exchange, a second exchange, a trunkline connecting said exchanges, a vrepeater` in each exchangeterminating said tr'unk line,` subscriber `waystations on lsaid trunkline *between said exchanges, a pair of" trunk splittingy keys at eachlwaystation controlling th'eucontinuity 'of said trunk line betweensaid'exchanges, means responsiveto the operation of the-first of saidvtrunk keys at any waystation lin initiating a call `overy said trunkline to Asaid first exchangefr splitting 'saidl

